VANCOUVER, British Columbia  A Canadian smelter produced most of the lead, zinc and cadmium pollution found in a Washington state lake at the center of a cross-border environmental fight, according to a study released Monday.

The U.S. Geological Survey said studies of sediment in Lake Roosevelt also determined that slag that was dumped into the Columbia River for decades had evidence of weathering and breaking down, and could not be considered inert.

The lake, which was created on the Columbia River in 1941 with the building of the Grand Coulee Dam, is the focus of a fight between the U.S. government, Washington state Indian tribes and Canadian mining firm Teck Cominco Ltd.

U.S. officials and the Confederation of Tribes of Colville Reservation want Teck Cominco to pay for a study and clean-up of the pollution under the jurisdiction of the U.S. "Superfund" law.

The company says it is willing to pay $13 million for a study of the pollution danger, but opposes doing it under U.S. law because the smelter is located in Trail, British Columbia, and subject to Canadian law.

ADVERTISEMENT

Teck argues that the U.S. law could open it up to millions of dollars in liability, but without the same protections that U.S. companies enjoy.

The company has also argued that the sand-like slag does not pose a health risk, and that there were other sources of pollutants found in Lake Roosevelt's sediments.

"These and other results from our study indicate that the liquid effluent from the Teck Cominco smelter is the primary contributor of the large concentrations found in sediment samples from the middle and lower reaches of Lake Roosevelt," the USGS said in a news release.

Teck Cominco officials were not available for immediate comment Monday.

The Colville tribes said the study proves the slag has had a negative impact on the environment.